Pattern measurement apparatus and pattern measurement method

1. A pattern measurement apparatus comprising: a beam intensity distribution creation unit configured to scan a charged particle beam over a reference pattern formed on a sample to create a line profile of the reference pattern, and create a reference-beam intensity distribution in which the charged particle beam is regarded as a reference beam, the reference pattern having edge portions formed at a right angle to a horizontal plane; an edge width detection unit configured to determine line profiles for pattern models by use of the reference-beam intensity distribution, and calculate edge widths reflecting an influence of a width of the reference beam, the pattern models including edge portions formed at various inclination angles; and a correspondence table creation unit configured to calculate correction values for edge positions from the calculated edge widths and the pattern models, and create a correspondence table in which the edge widths and the correction values are associated with one another.

2. The pattern measurement apparatus according to claim 1 , wherein the beam intensity distribution creation unit further creates the reference-beam intensity distribution so as to include a first distribution on a first side of an intensity distribution at a rising point of the reference pattern and a second distribution on a second side of an intensity distribution at a falling point of the reference pattern, the first and second sides being located at which the reference pattern is not formed.

3. The pattern measurement apparatus according to claim 2 , wherein the edge width detection unit further creates the line profiles for the pattern models including the edges formed at the various inclination angles by combining the line profile of the reference pattern and corresponding line profiles of edge portions, the line profiles of corresponding edge portions being created by calculating amounts corresponding to overlaps between the reference beam and the edge portions under assumption that an electron beam having the reference-beam intensity distribution is applied to the pattern models in a scanning manner.

4. The pattern measurement apparatus according to claim 3 , further comprising a line width measurement unit configured to measure a line width of a pattern, wherein the line width measurement unit measures an edge width and edge positions of a pattern formed on a sample, sets the edge width and the edge positions as a temporary edge width and temporary edge positions, detects a correction value for each of the temporary edge positions by referring to the correspondence table, and corrects each of the temporary edge positions by using the correction value to thereby calculate the line width of the pattern.

5. The pattern measurement apparatus according to claim 4 , wherein the correspondence table creation unit further creates an edge width correspondence table in which edge widths of the pattern models and the edge widths calculated by the edge width detection unit are associated with one another, and the line width measurement unit calculates an inclination angle of each edge of the pattern based on a height of the pattern and a real edge width which is determined by referring to the edge width correspondence table for the temporary edge width.

6. A pattern measurement method comprising the steps of: scanning a charged particle beam over a reference pattern formed on a sample to create a line profile of the reference pattern, the reference pattern having edge portions formed at a right angle to a horizontal plane; creating a reference-beam intensity distribution in which the charged particle beam is regarded as a reference beam on the basis of the line profile; creating line profiles for pattern models on the basis of the reference-beam intensity distribution, the pattern models including edge portions formed at various inclination angles; creating differential profiles by differentiating the line profiles; calculating edge widths reflecting an influence of a width of the reference beam based on the differential profiles; and calculating correction values for edge positions from the calculated edge widths and the pattern models, and creating a correspondence table in which the edge widths and the correction values are associated with one another.

7. The pattern measurement method according to claim 6 , wherein the step of creating the reference-beam intensity distribution includes a step of creating the reference-beam intensity distribution by combining a first distribution on a first side of an intensity distribution at a rising point of the reference pattern and a second distribution on a second side of an intensity distribution at a falling point of the reference pattern, the first and second sides being located at which the reference pattern is not formed.

8. The pattern measurement method according to claim 7 , wherein the line profiles for the pattern models including the edges formed at the various inclination angles are each created by combining the line profile of the reference pattern and line profiles of corresponding edge portions, the line profiles of corresponding edge portions are created by calculating amounts corresponding to overlaps between the reference beam and the edge portions under assumption that an electron beam having the reference-beam intensity distribution is applied to the pattern models in a scanning manner.

9. The pattern measurement method according to claim 8 , further comprising the steps of: measuring an edge width and edge positions of a pattern formed on a sample and setting the edge width and the edge positions as a temporary edge width and temporary edge positions; detecting a correction value for each of the temporary edge positions by referring to the correspondence table; and correcting each of the temporary edge positions by using the correction value to thereby calculate a line width of the pattern.

10. The pattern measurement method according to claim 8 , further comprising the steps of: creating an edge width correspondence table in which edge widths of the pattern models and the edge widths calculated by the edge width detection unit are associated with one another; detecting a real edge width corresponding to the temporary edge width by referring to the edge width correspondence table; and calculating an inclination angle of each edge of the pattern based on a height of the pattern and the real edge width.